Rhodotorula glutinis

Rhodotorula glutinis is the type species of the genus Rhodotorula, a basidiomycetous genus of pink yeasts, which contains 370 species. Heterogeneity of the genus has made its classification difficult with five varieties having been recognized, however as of 2011 all have been considered to represent a single taxon. R. glutinis is an aerobic yeast characterized by pink, smooth colonies with a moist appearance. Reproduction is typically by multipolar budding although pseudohyphae are occasionally produced.

It normally grows at 37 °C at a rapid rate, and requires a minimum water activity of 0.92, pH of 2.2, and organic acids or HCl. Growth is inhibited by 100 mg/kg or less of benzoic acid or sorbic acid and a pH of 4 or above. The fungus is unable to grow on malt acetic agar or MY50G medium. At maturity, the cells reach a diameter of 3-5 µm and are round, oval, or elongate in shape, aggregating as mucoid colonies. Carbohydrates in the cell include glucose, fucose, galactose, and mannose.

Standard microbiological methods of identification have misidentified Candida auris as Rhodotorula glutinis, until sequence analysis correctly identified C. auris as such. The genome of R. glutinis is CG-rich, containing up to 67% GC by base composition. R. glutinis is distributed widely, most often found in soil, air and throughout the phyllosphere. Accordingly, it is not uncommon to recover it in cultures of cereals, flour, malting barley, dough, citrus products, olives and soaking soybeans.

There has been increasing interest and development in the biotechnological applications of R. glutinis over recent years. The fungus produces carotenoids, such as beta-Carotene and torularhodin, which animals cannot synthesize on their own. In the yeast, carotenoids act as a protective agent against visible light and harmful metabolic oxygen species. Carotenoids are valuable in wastewater treatment, enzyme production, pharmaceuticals, and even tumour inhibition.

Gareth

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